This application proposes a thorough study of the stages of development of the nose and ear using Xenopus laevis as a model system. Studies including fate mapping, embryo transplantation and explantation experiments will define the early tissue interactions that lead to the formation of the olfactory epithelium. The experiments in the auditory system will focus on tissue interactions that lead to formation of the highly regionalized tissues within the inner ear. These experiments will provide information on the hypothesis that all sensory tissues are determined by common mechanisms and will provide a basis for undertaking studies to identify the signaling molecules that control sensory tissue development.